At the Conservative conference in Birmingham this week the chancellor claimed a further £16bn of savings must be found by 2015/16 to meet his target of balancing the budget within five years.

This, he said, would include cutting £10bn more from the welfare bill by 2016-17, on top of the £18bn announced in 2010.

'Sacrifices'

Asked about the prospect of further cuts, Mr Clegg said: "The idea that of that £16bn we're just going to scoop out £10bn from welfare - which will inevitably hit the poorest before asking anything of the wealthiest - no. Flatly no."

Analysis

By Norman SmithChief political correspondent, BBC News Channel

So is the coalition heading for a major bust-up over benefit cuts?

Well, probably not.

Despite the uncompromising language there's a large degree of rather deliberate shadow boxing going on.

It all comes down to dates and numbers.

Mr Clegg has indeed pledged to oppose to £10bn worth of welfare cuts but this applies only to the first year of the next spending round (2015-16).

Mr Osborne is looking for £10bn of cuts over the first two years of the next spending round (2015-17).

Hence its easy to see how political honour can be observed on all sides.

Phase the £10bn worth of welfare cuts over two years and ..... Hey presto!

Mr Osborne gets his £10bn and Mr Clegg keeps his promise.

The important political point - which both men are absolutely agreed on - is that there will have to be more welfare cuts.

The country needed to carry on "tightening its belt" for some time into the future, Mr Clegg said, but those at the top should be asked to contribute first.

"I start from a very simple principle that when we're all having to make sacrifices... you ask people at the top and then you work down.

"You don't ask people at the bottom and then work up."

He continued: "I think it's unrealistic to assume that you can't make any more savings from welfare... but it hasn't been agreed in government.

"I certainly don't agree with this idea that you just pluck a £10bn figure out of the sky and say 'that's what we're going to do' without asking how you can do that more fairly."

During his conference speech Mr Osborne said the better off would pay more in taxes, but the budget could not be balanced "on the wallets of the rich".